Hyde S R, McCallum R E
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
Infect Immun. 1992 Mar;60(3):976-82. doi: 10.1128/iai.60.3.976-982.1992.
Previous work in our laboratory demonstrated increased sensitivity of senescent (24-month-old) mice to cecal ligation and puncture (CLP) sepsis compared with that of mature (12-month-old) mice. In this study the median lethal dose of the strain of Escherichia coli most frequently isolated during CLP sepsis was determined. No significant age-associated difference in the mean lethal dose or the mean survival time was noted; however, sham surgery before injection of E. coli decreased the mean lethal dose by at least 100-fold. With surgical manipulation, the average time to death after bacterial injection simulated more closely that observed after CLP surgery. Host responses to CLP sepsis were investigated by measuring the levels of corticosterone, glucose, and tumor necrosis factor (TNF) in the sera of mature and senescent mice at 2-h intervals after surgery. Corticosterone levels increased gradually during the course of sepsis in mature mice; however, senescent mice demonstrated a pronounced elevation in hormone levels at 2 and 4 h after surgery. At subsequent sampling intervals the corticosterone levels remained elevated, although they were similar for both ages. At all sampling intervals, the glucose levels in serum were lower in senescent mice than in mature mice. Pronounced hypoglycemia (less than 80 mg/dl) was observed in senescent mice at 8 h postsurgery. TNF was detected in serum within a narrow time frame in both age groups at 6, 8, and 10 h postsurgery. Although elevated TNF levels in serum were not seen in every mouse in each group (approximately 50%), the data hinted that senescent animals produced larger quantities of TNF during CLP sepsis than did mature animals. E. coli lipopolysaccharide (1 mg/kg) was injected intraperitoneally, and the TNF levels in serum and peritoneal lavage fluid were measured at 30, 60, and 90 min. Senescent mice demonstrated a level of TNF in serum at 90 min after lipopolysaccharide treatment that was 20-fold higher than that of mature mice (299,877 pg/ml versus 15,594 pg/ml). The amount of TNF produced locally in the peritoneum was also substantially higher in senescent mice than in mature animals (1,716 pg/ml versus 776 pg/ml). The increased production of TNF in senescent animals, despite elevated circulating corticosterone levels, suggested an age-related defect in glucocorticoid-directed downregulation of TNF production. This was confirmed in lipopolysaccharide-treated animals given exogenous dexamethasone.(ABSTRACT TRUNCATED AT 400 WORDS)
我们实验室之前的研究表明，与成熟（12月龄）小鼠相比，衰老（24月龄）小鼠对盲肠结扎穿刺（CLP）脓毒症更敏感。在本研究中，测定了CLP脓毒症期间最常分离出的大肠杆菌菌株的半数致死剂量。未观察到平均致死剂量或平均存活时间与年龄相关的显著差异；然而，注射大肠杆菌前进行假手术可使平均致死剂量降低至少100倍。通过手术操作，细菌注射后至死亡的平均时间更接近CLP手术后观察到的时间。通过在手术后每隔2小时测量成熟和衰老小鼠血清中皮质酮、葡萄糖和肿瘤坏死因子（TNF）的水平，研究宿主对CLP脓毒症的反应。成熟小鼠在脓毒症过程中皮质酮水平逐渐升高；然而，衰老小鼠在手术后2小时和4小时激素水平显著升高。在随后的采样间隔中，皮质酮水平一直保持升高，尽管两个年龄组的水平相似。在所有采样间隔中，衰老小鼠血清中的葡萄糖水平均低于成熟小鼠。衰老小鼠在手术后8小时出现明显低血糖（低于80mg/dl）。在两个年龄组中，均在手术后6、8和10小时的狭窄时间范围内在血清中检测到TNF。尽管每组并非每只小鼠血清中的TNF水平都升高（约50%），但数据表明衰老动物在CLP脓毒症期间产生的TNF量比成熟动物多。腹腔注射大肠杆菌脂多糖（1mg/kg），并在30、60和90分钟时测量血清和腹腔灌洗液中的TNF水平。脂多糖处理90分钟后，衰老小鼠血清中的TNF水平比成熟小鼠高20倍（299877pg/ml对155
